The floor of my Sierra Designs tent and the rainfly are very sticky. I've stored both loosely packed for about twelve years on a shelf in a closet close the the ceiling where heat gets trapped. It can get quite warm there at times, so I believe the heat has broken down the material over the years. I tried airing out the tent and rainfly in the sun and washing both in cold water with a mild detergent, but these made little difference. Is there anything I can do to rehabilitate them?

The polyurethane (PU) coating has begun to return to its component parts. After all, it is poly - UREA-thane. (Of course, being organic chemistry, it is much more complicated than that.) That's why it smells like dog vomit.

Short answer: either get a new tent or replace the floor and fly with new material - maybe silnylon - which will not rot on the shelf. Carefully remove the stitching from the existing fly and floor and use the pieces as patterns, taking care to align the direction of the weave. Plain old silnylon will weigh much less than the old fabric which, in addition to rotting, has probably absorbed atmospheric moisture.

Good idea. No reason to get rid of the tent if I can just replace the floor. I really like the tent, and it's little used. Seems like I could just spray the thing with some kind of water repellent coating, but I'm sure that's just wishful thinking because the material is probably deteriorated. I'll get to work on replacing the floor. Is Thruhike.com a good source for material? Thanks for all the helpful replies.

One more thing: If the PU has not deteriorated too far, that is, if it is sticky and stinky rather than dry and cracked, you may be able to restore it temporarily - for a few uses - by throwing it in a medium drier for 15 minutes.